Update JRuby to leverage pure-Ruby DSL.

JRuby unit and conformance test fixes.
diff --git a/ruby/lib/google/protobuf.rb b/ruby/lib/google/protobuf.rb
index 9368768..a68154d 100644
--- a/ruby/lib/google/protobuf.rb
+++ b/ruby/lib/google/protobuf.rb
@@ -51,9 +51,10 @@
     require 'google/protobuf_c'
   end
 
-  require 'google/protobuf/descriptor_dsl'
 end
 
+require 'google/protobuf/descriptor_dsl'
+
 require 'google/protobuf/repeated_field'
 
 module Google